Process of producing gibberellic acid by cultivation of gibberella fujikuroi



United States Patent;

poration of Great Britain 'No nrawing. A nc'afionaanuary 31,1958

' Serial No. 712,338 laims priority, application Great Britain February 13, 1957 Claims. (Cl. "195- 36) This invention relates to improved metabolic processes, in particular to metabolic processes used for the production of gibberellic acid.

Gibberellic acid'is'aiplant growthstiriiulant obtainable from the culture filtrates of certain active strains of the fnould 'Gibbe'rl'la fujikuroi (Fusar'iu'm; mo'nilifor'me). It is known tomanufacture gibberellic 'acid'by cultivating an active'strain of Gibberella fujikuroi in a suitable'stir'r'ed and aerated nutrient medium containing a source of carbon for example-glucose, a source of nitrogenfor'exampl'e ammonium nitrate, certain metallic salts for example magnesium sulphate and potassium dihydro'gen phosphate and traces of metals such as iron, copper, 'zi'nc, manganese and molybdenum. It is a characteristic of this'inet'abolic process that the acid is producedfor the most part when net protein'synthsis or active growth 'of the mould has been checked. This check in active growth maybe the result of exhaustion of one of the 'essentialconstitue'nts of the nutrient solution, e.'g. nitrogen or carbon.

When active growth of the 'mould is checked by exhaustion of an essential constituent of the medium it is preferred that this essential constituent is not the 'carbon source; indeed'it "is preferred that carbon-remains available to satisfy the-requirefiieiits of-the mould durin'g the gibberellic acid production stage. 'Within limits the more carbon there is-aVaiIabIe during-the acid production stage the higher is likely to be the gibberellic acid production. However, a high concentration of carbon, =particulai'ly when in the form of sugar, in the initial stage-emu: metabolic process is likely to retard therate of growth of the mould'an'd consequently have. an 'adverseeflect on the overalle'fliciency of'the process.

According to the present invention in a metabolic process for the production ofgibber'ellic acid by cultivating an active "strain of Gibberella "fujikuro'i and checking active growth to promote gibberellic acid production, carbon availability is maintained during the gibber'llic'acid pm duction stage 'byadding asourc'eof carbon to themedium.

The source of carbon may be added continuously or batchwise at intervals and 'a suitable source of carbon may be a sugar for example sucrose or glucose, ap'ol'yhydric alcohol for example glycerol or esters thereof, 'or a vegetable oil.

The source of nitrogen used in the medium may -be anammoniumfsalt, 'a nitrat'e, 'corn steep liquor'or'a digest assimilable nitrogen.

Hyfnie'ans o'i the inventionwehave found it possible to initiatea'hig'h active growth of thc'mould and yet satisfyits carbon requirements'during the gibberellic acid production stage. w

mu invenubn is illustrated by the following. Two refines-tars, A a'nd'B, wereset up, each with 30 litres of a medium containing:

.Fer- Fermentcr A menter A Gluc'o's'e 'iiio'ilohydtate percent w./v 10' 10 Ammonium nitrate do- 0.48 0. 24 Potassiuin dihydrog'n H o a 0.5 0.5 Magnesium sulphate heptahydr'ate. .do 0. 1 0. 1 Minor'element concentrate .perent v./v 0. 2 0.2

. 'lhe composition of the minor element concentrateis as fo w Ferrous sulpha-te' heptahydrateiumua gm 0.1 Coppe siilphate pentahydratm gm c 0.015 Zinc sulphate"heptahydratemmr; gm" 0.1 ManganeS'e'suIphateheptahydratm g'm 0.01 Potassium molybdate ('K2MO04) ml 0.01 Water m1 100 'Ihe-mediawere inoculated with an active strain of G i lybcifella fuji-kurpi (samplesdeposited in the culture collections of the Commonwealth Mycological Institute, Kew, the B ureau voor Schimmelcultures, Baarn, andthe Northern Utilisation Researchand Development Division of theUnited'States Department of Agriculture, Peoria,

v Illinois,"U;S.A.), and were maintained'at a temperature of: 262 C., air being blown into the media at a rate of 1 litres/minute. After fermentation had'proceeded for l18 ,h ou1s, by which time active growth had been substantially checked by exhaustion of nitrogen in the media, glucose monohydrate was added aseptically in lots of 150 grams to maintain the sugarconcentration in the media above 2% W./v.

Thefol lowing'tableshows the total sugar used by the mould and the gibberellic acid concentration in the two mediaas cultivation proceeded.

,1. i Gibberellic acid in .1 'Su arused Tiine thours after 1 g/l inoculation) 3 Fermenter 'Fermenter Fermenter. Fermenter A B A B 48 5 5 69--" 11 12 76 15 .16 9'3 44. .25 99- 57 29 117-- '98 52 11q 98 .56 106 56 I 129, 68 148 135 69 153 78 157 v79 172 87 193 .209 .109 219. 246 109 278 -.'.1 265 gl67. =355 23T The medium used in fermenter A was substantially balanced with respect to carbon and nitrogen, i.e. it contained these two nutrients in the approximate proportions in which they are taken up by the actively growing mould. Consequently the carbon would be exhausted at about the same time as the nitrogen and in the absence of additions of nutrients the gibberellic acid subsequently produced could not have been expected to exceed 120 mg./litre. The table shows however that when additions of a source of carbon, in this case glucose monohydrate, are made after cessation of active growth, gibberellic acid production can be maintained at least until the concentration rises to 324 mg./ litre.

In the case of fermenter B the medium initially contained excess carbon which was still available when the nitrogen content had been exhausted and normal gibberellic acid production would have been expected to be as much as 240 mg./litre. However, additions of sugar to maintain carbon availability resulted in the acid concentration rising to 409 mg./litre.

The medium used for the active growth stage of the mould is a so-called balanced medium wherein the concentration of nitrogen may be within the range of 0.017- 0.26% w./v. for example in the form of ODS-0.75% w./v. of ammonium nitrate and preferably within the range of 0.07-0.17% w./v. of nitrogen for example in the form of 0.2-0.5% w./v. of ammonium nitrate. The concentration of carbon for example in the form of sucrose, glucose or glycerol is then chosen to provide a medium wherein the ratio of carbon to nitrogen prefer ably lies between the values of :1 and 25: 1. A typical balanced medium suitable for active growth may contain for example 0.24% w./v. of ammonium nitrate and 3.18% w./v. of glucose monohydrate, i.e. a ratio of C:N of 14:1 or it may contain 0.48% w./v. of ammonium nitrate and 10% w./v. of glucose monohydrate, i.e. a ratio of C:N

When active growth is substantially checked by exhaustion of nitrogen in a balanced medium, there is little or no excess carbon remaining in the medium and there is thus little or no carbon from which the mould can produce gibberellic acid. This is the stage at which an additional source of carbon is added to the medium in order to sustain the production of gibberellic acid.

The amount of carbon source added to the medium at the end of the active growth stage is controlled in order to prevent inhibition of the mould in its production of gibberellic acid. A large excess of carbon source is disadvantageous in the acid production stage and a reasonable excess may be for example in the form of between 0.1 and 10% w./v. of glucose and more particularly in the form of between 1 and 4% w./v. of glucose.

The process with which this invention is concerned may be used in conjunction with a multistage process for the production of gibberellic acid as described in our copending application No. 712,337. Thus the cultivation of the active strain of Gibberella fujikuroi may be carried out in two or more stages, preferably at least three stages, the first stage being one of active growth of the mould in an approximately balanced medium, i.e. the ratio of C:N in the medium is between 10:1 and 25: 1, the second stage being one in which active growth proceeds, in a medium containing a high ratio of C:N for example between about 3021 and about 55:1 and active growth is checked by exhaustion of nitrogen leaving an excess of the carbon source and the third stage being one in which additional quantities of the carbon source are fed into the medium keeping an approximately constant concentration of carbon source in the medium until the production of gibberellic acid ceases.

Thus for example, the first stage may be carried outiin a medium containing 3.18% w./v. of glucose monohydrate and 0.24% w./v. of ammonium nitrate i.e. aCzN ratio of about 14:1 and the second stage may then be carried out in an unbalanced medium of higher C:N

ratio for example a medium containing 16% w./v. or 10% w./v. of glucose monohydrate and 0.4% w./v. of am-- monium nitrate, i.e. a ratio of C:N of 41:1 or 26:1 respectively. The growth of the mould continues until the source of nitrogen is completely used up and there then.

duction of gibberellic acid begins.

steadily used up and when the said source reaches a con-- centration of about 0.5-10% w./v. of the medium, the: addition of further quantities of a carbon source, which. may or may not be the same as that used in the earlier stages, begins in order to maintain a constant concentration of carbon in the medium and thereby sustain continued production of gibberellic acid in yields which have not hitherto been attained.

The preferred source of carbon is a sugar for example sucrose or glucose and the preferred constant concentration of the said sugar during the continued production of gibberellic acid is in the range of about 1% to about 4% w./v. of the medium. The preferred constant concentration can be attained by adding quantities of sugar to the medium in the final gibberellic acid production stage at intervals for example at 12-24 hourly intervals. By this means there can be obtained a culture medium containing up to about 1000 mg. of gibberellic acid per litre of medium and the said acid can be isolated from the medium by known means.

The invention is further illustrated by the following examples:

EXAMPLE 1 Preparation of inoculum 5 litres of a nutrient medium containing glucose monohydrate 8% (w./v.), ammonium nitrate 0.4% (w./v.), potassium dihydrogen phosphate 0.5% (w./v.), magnesium sulphate heptahydrate 0.1% (w./v.) and a minor element concentrate 0.2% (v./v.), composition described earlier, at pH 3.47 is inoculated from an agar culture of Gibberella fujikuroi. The medium is maintained at 25 C. and is stirred and aerated with air at the rate of 2.5

. litres of air per minute.

PRODUCTION FERMENTATION After hours, 5 litres of the above culture are inoculated into a -litre fermenter vessel containing a nutrient medium prepared as follows:

Water to make up to 75 litres.

1 The composition of the minor element concentrate is that given above.

The medium is sterilised and then cooled and inoculated with 5 litres of the inoculum as described above. The medium is stirred and maintained at a temperature of 1 26 C. and is aerated with an air flow of 0.5 volume of air-per volume of culture medium per minute. When active growth of the'mould has ceased, i. e. when the nitrogen source is completely used up, production of gibberellic acid begins, and the remaining source of carbon (glucose) rapidly diminishes in concentration. After 39 hours from the beginning of the formation of gibberellic acid in the acid production stage, the glucose concentration is about 0.9% w./v. and thus additional quantities of sugar are added to the nutrient medium at 12- hourly intervals, in order to maintain a concentration of approximately 2% w./v. of glucose in the nutrient medium throughout the remainder of the acid production stage of the fermentation. The following table shows the concentration of gibberellic 1 acid :in the :medium in 'relation tothe glucose=consumed as fermentation proceeds:

hydrate and 0.4% w./v. of ammonium nitrate. During the gibberellic acid production stage, the excess glucose present in the nutrient "medium is rapidly used up and additional quantities 'of glucose monohydrate are added at 12 hounly intervals, after about 74 hours, in order to maintain a concentration of approximately 4% W./v. of glucose in the nutrient medium throughout the remainder of the gibberellic acid production stage of 'thefermentation. The following table shows the concentration of gibberellic acid in the medium in'relation to the glucose consumed as fermentation proceeds:

Gibberellic Sugar Age (hours after inoculation) aci used (mg. (percent litre) w./v.)

Example 3 The process described in Example 1 is repeated exglucose monohydrate are added 'at 1-2-'hourly intervals, after about 26 hours, :in orderto maintain a concentration'of approximately 10% W.'/-V. 0f .gluOS6 in the nutrient'm'ediumthroughout?theremainderof the gibberellic 5 acid productionstage'offthe fermentation. The following p 7 H it jgfibg g' mg "f table shows the concentration of gibberellio acid in the Age (hours after ocu a fig medium in relation to the glucose consumed as fermentaj 'yf jj .3. tion proceeds:

43 1231 49 10 Gibberellie Sugar 71 .105. 6.8 Age (hours after inoculation) acid. used 144 .268 10. 6 (mg. (percent 191- 352. 12.1 litre) w.lv.) e a:

30 15 52. '67 9.4 64. 11.2 The fermenter contents are; then filtered and a sample 76 121 (58 litres) of the filtrate isextracted with ethyl acetate 8 121 13.7 on 14.2 to remove glbberelhc acid wh ch is then recovered by 112 192 v14.8 known means. Thereis thus-obtained 33.48 gm. of g1b- 2O 13% 323- ii; berellic acid has a colourless crystalline powder, M.P. 148 261 17.6 233235 C. With decomposition. -A second crop of gg g-g gibberellic acid canb'e obtained from the crystalline fil- 220 gm trate 24 383 22.6 256 445 23.2 mp 2 268 52o 24.0 293 541 25.6 The process described in Example 1 1s repeated ex- 304 546 26.5 cept that the 8% w./v. of glucose monohydrate and 32:? 0.24% 'w./v. of ammonium nitrate in "the nutrient medium 460 794 33 7 used for the gibberellic acid production stage of the 2g; gig at: fermentation are replaced by 20% w./v. of glucose mono- 30 580 905' 35in Example -4' The process described in Example l is'repeated except that the 8% w./v. of. glucose monohydrate and 0.24% w./v. of ammonium nitrate-arereplac ed by 16.0% w./v. of glucose monohydrate and 04% w./-v. of ammonium nitrate. During the gibberellic acid "production stage of the fermentation, the excess vglucosevpresent in the nutrient mediumis-used up and'additio'na l quantities of glucose monohydrate are addedafter 162 hours and thereafter at 1224 hourly intervals, 'inforder1to maintain a concentration of approximately 13% w./-v.-of glucose in the nutrient medium throughout the remainder of the acid production stage of the fermentation. The -follow ing table shows the concentration of gibberellic acid in the medium in relation to the glucose concentration as fermentation proceeds:

. Gibherellic Concert- Age (hours after inoculation) acid tration of I (mg/litre) sugar (percent wJv.)

The gibberellic acid is isolated by known means by filtration of the fermentation medium and passage of the Glbberemc (30mm. filtrate (63 litres) through carbon. The adsorbed gibge (hours afterlnowlfltlon) gfi t fg berellic acid is removed by elution and recovered and purified by crystallization. There is thus obtained 63.0 gm. 5 of gibberellic acid as a colourless crystalline product, 16 10,58 M.P. 233235 C. with decomposition. :2 -g Example 5 23 12 21 64 29 4.87 The process described in Example 1 is repeated ex- 69 8g 2.3; cept that the 8% w./v. of glucose monohydrate and g; 128 1 0.24% w./v. of ammonium nitrate are replaced by 20% 93 lg: gig w./v. of glucose monohydrate and 0.4% w./v. of am- 1 2: 4 monium nitrate. During the gibberellic acid produc- 114 225 6 276 2.54 tion stage of the fermentation, the excess glucose present 15 293 176 in the nutrient medium is used up and additional quan- 160 23g tities of glucose monohydrate are added after 154 hours $3; 491 77 and thereafter at 12 hourly intervals, in order to main- 232 255 569 4.6 mm a concentration of approximately l4% w./v. of glu- 2% 590 4.04 cose in the nutrient medium throughout the remainder 304 122 698 2. 79 of the acid production stage of the fermentation. The 762 2.84 following table shows the concentration of gibberellic 376 825 .41 400 901 2.16 acid 1n the medlum in relation to the glucose concen- 424 0.84 tration as fermentation proceeds: 25 2% 35; 8:22 496 989 0. 26 m 0. 21 Glbberellic Concen- Age (hours after inoculation) acid tration of (mg-mire) sugtflper' The gibberellic acid is isolated by known means by can filtration of the fermentation medium and passage of the 9 18.25 30 filtrate (60 litres) through carbon. The adsorbed gib- 17.97 berellic acid is removed by elution and recovered and g; g purified by crystallisation. There is thus obtained 63.6 63 15:43 gm. of gibberellic acid as a colourless crystalline solid, $3 g 3% M.P. 233-235" C. with decomposition. 11s 79 61 86 What we claim is:

2Z 1. A metabolic process for the production of gibberel- 154 229 3.84 lic acid by cultivating an active strain of Gibberella ii? iii 2', S? fujikuroi and checking active growth to thereby promote 0 4.09 gibberellic acid production, wherein carbon availability 3?: 21 is maintained during the gibberellic acid production stage 226 4.09 by adding a source of carbon to the medium. 323 22 213% 2. Process as claimed in claim 1 wherein the source 262 427 of carbon is selected from the group consisting of 32% 13% 3 sucrose, glucose, glycerol, glycerol esters and vegetable 2oz 519 3.13 il,

23? 3:93 3. Process as claimed in claim 1 wherein the said mediggg 23% 5-3 vum includes a source of nitrogen selected from the group 353 623 consisting of an ammonium salt, a nitrate, corn steep 3 g 2;? $3 liquor and peptone. 3 660 4. Process as claimed in claim 1 wherein the active 392 22g growth stage is carried out in a balanced medium having 4% 669 concentration of nitrogen within the range of 0.017- 442 669 Q84 0.26% w./v. is? 333 81%;; 5. Process as claimed in claim 4 wherein the nitrogen 2;; 825 is in the form of ammonium nitrate of a concentration 562 809 :::I of 0.05-0.75% w./v. 585 312 6. Process as claimed in claim 4 wherein the ratio of carbon to nitrogen is within the range of 10:1 and 25:1. Example 6 6O 7. Process as claimed in claim 6 wherein the carbon is The process described in Example 1 is repeated except in the form of 10% w./v. of glucose monohydrate and that the 8% w./v. of glucose monohydrate and 0.24% the nitrogen is in the form of 0.48% w./v. respectively w./v. of ammonium nitrate are replaced by 10% of ammonium nitrate. w./v. of glucose monohydrate and 0.4% w./v. of am- 8. Process as claimed in claim 1 wherein the concenmonium nitrate. During the gibberellic acid production tration of carbon in the medium during the acid producstage of the fermentation, the excess glucose present in tion stage is in the form of between 0.1% and 10% w./v. the nutrient medium is used up and additional quantities of glucose. of glucose monohydrate are added after 60.5 hours and 9. Process as claimed in claim 1 which is carried out thereafter at 12-24 hourly intervals, in order to mainin at least two stages, the first stage being one of active tam a concentration of approximately 24% w./v. of growth in a balanced medium wherein the ratio of carbon glucose in the nutrient medium throughout the remainder to nitrogen is between 10:1 and 25:1, the second stage of the acid production stage of the fermentation. The being one of active growth in an unbalanced medium following table shows the concentration ofgibberellic acid wherein the ratio of carbon to nitrogen is between about in the medium in relation to the glucose concentration as g 30:1 and about 55 :1 until checked by exhaustion of nitroferm n atlon P oc d l gen and any subsequent stage being one in which addi 9 tional quantifies of the carbon source are added to the medium in order to maintain an approximately constant concentration of carbon source.

10. Process as claimed in claim 9 wherein the approximately constant concentration of carbon source is be- 5 tween 0.5% and 10% W./v. of the medium.

Hutchinson July 19, 1932 Waksman et a1. Feb. 5, 1946 Bernhauer et a1. Mar. 15, 1932 10 10 2,842,051 Brian et a1. July 8, 1958 2,865,812 Borrow et a1. Dec. 23, 1958 OTHER REFERENCES Yabuta: Chemical Abstracts, 34, 1940, 3314.

Yabuta: Chemical Abstracts, 44, 1950, 10814.

Gross et al.: Chemistry aand Industry, Aug. 23, 1954, p. 1066.

Gross et al.: Jour. Chem. 800., December 1954, pp. 4670-4676.

Stodola et al.: Arch. of Biochemistry, 54, January 1955, pp. 240-245. 

1. A METABOLIC PROCESS FOR THE PRODUCTION OF GIBBERELLIC ACID BY CULTIVATING AN ACTIVE STRAIN OF GIBBERELLA FUJIKUROI AND CHECKING ACTIVE GROWTIH TO THEREBY PROMOTE GIBBERELLIC ACID PRODUCTION, WHEREIN CARBON AVAILABILITY IS MAINTAINED DURING THE GIBBERELLIC ACID PRODUCTION STAGE BY ADDING A SOURCE OF CARBON TO THE MEDIUM. 